Field of the Invention
The present invention relates to an optional device for an electrical machine and to an electrical machine.
Discussion of the Background
Electrical machines such as image forming apparatuses emit exhaust gases that contain ultrafine particles (UFPs) of siloxane, which results from heating of silicon, or hydrocarbon, which results from melting of toner at high temperatures. In recent years, stricter regulations have been imposed on ultrafine particles. This requires the electrical machines to use a filter or a similar device to collect ultrafine particles in the exhaust gas and to discharge purified air to the atmosphere. Newly developed electrical machines are designed to satisfy this requirement against ultrafine particles in the exhaust gas. In order for existing electrical machines to satisfy the requirement, a discrete, optional device that has a function to purify the exhaust gas may be added to the existing electrical machines.
The optional device can be powered directly by a commercial power source, instead of by the electrical machine. It is necessary, however, to electrically connect the electrical machine and the optional device to each other in order for the electrical machine to send the optional device electrical signals to control operation of the optional device.
In an exemplary case of an image forming apparatus, while the image forming apparatus is in waiting mode, an exhaust fan is out of operation or rotating at speeds so low that the amount of exhaust gas is negligibly small. Thus, the amount of ultrafine particles in the exhaust gas is negligible. While the image formation unit is in operating mode, the exhaust fan is rotating at full speed, emitting a larger amount of exhaust gas, which contains a larger amount of ultrafine particles. This necessitates control that includes sending the optional device an electrical signal to determine whether the image forming apparatus is in waiting mode or operating mode and making the optional device effect its air purification function while the image forming apparatus is in operating mode.
In order to implement the electrical connection, however, it is necessary to provide, in advance, the electrical machine with an interface (such as a connector) to make the electrical connection with the optional device possible. Providing the interface leads to an increase in cost. For an existing electrical machine without such interface, it is necessary to modify the electrical machine so as to retrieve the electrical signal and implement the electrical connection with the optional device.
In view of this situation, the inventors worked on the development of an optional device that has an air purification function and that can be discretely mountable to image forming apparatuses while eliminating the need for electrical connection. This optional device includes an air flow sensor and a controller. The air flow sensor detects exhaust gas from the image forming apparatus. The controller controls the operation of the air purification function (the operation of an electric fan) based on a detection signal from the air flow sensor. That is, the optional device determines how the image forming apparatus is operating by detecting the exhaust gas from the image forming apparatus, instead of by receiving an electrical signal from the image forming apparatus. This enables the optional device to turn the air purification function into operation at any desirable time.
Japanese Unexamined Patent Application Publication No. 11-84534 discloses a similar optional device for a liquid crystal projector instead for an image forming apparatus. This optional device measures the speed of cool air flow using an air speed sensor and turns off a power source, such as an optical source, based on a detected value of the measured air speed. In this manner, the optional device protects the liquid crystal panel. In this conventional optional device, the air speed sensor is arranged at an exit port of the liquid crystal panel for the cool air flow. This arrangement is intended to eliminate or minimize the influence of the air flow from the exhaust fan and thus to optimize the measurement of the speed of the cool air flow.
In the conventional optional device, the air flow sensor is arranged between the cooling fan of the image forming apparatus and the electric fan of the optional device. This arrangement makes it difficult to detect the presence or absence of the exhaust gas (air flow) from the image forming apparatus while the electric fan of the optional device is in operation. That is, even if there is no exhaust gas from the image forming apparatus, the air flow sensor may possibly erroneously detect an air flow caused by the electric fan of the optional device as the exhaust gas from the image forming apparatus.
Japanese Unexamined Patent Application Publication No. 11-84534 recites that in the optional device for a liquid crystal projector, the air speed sensor is arranged at the exit port of the liquid crystal panel for the cool air flow and that this arrangement minimizes the influence that the air flow from the exhaust fan has on the air speed sensor. However, in optional devices for image forming apparatuses, the air flow sensor has to detect smaller amounts of exhaust gas from the image forming apparatus. Therefore, arranging the air flow sensor adjacent to the exhaust port of the image forming apparatus is not enough to sufficiently diminish the influence of air flow from the operating electric fan of the optional device.
It is an object of the present invention to provide an optional device for an electrical machine that deals with the above-described circumstances. Specifically, the optional device includes an air flow sensor and an electric fan. The air flow sensor detects the presence or absence of an exhaust gas from the electrical machine. The electric fan is controlled in accordance with a detection signal from the air flow sensor. Even while the electric fan of the optional device is in operation, the optional device sufficiently diminishes the influence of the air flow from the electric fan, and thus enables the air flow sensor to accurately detect the presence or absence of the exhaust gas flowing from the electrical machine.